Bags made of thin polyethylene material have been used in various sizes. Small bags are used in packaging of sandwiches and the like. Larger bags are used as shopping bags. Even larger bags ar used for containing trash.
A particularly advantageous closure for such a bag includes a draw tape made from the same polyethylene material as the bag. U.S. Pat. No. 3,029,853--Piazzi, British Patent No. 1,125,363 Jortikka, U.S. Pat. No. 3,738,568--Ruda, U.S. Pat. No. 4,558,463--Boyd and U.S. Pat. No. 4,624,654 Boyd et al are examples of draw tape bags. Such closures have been successfully employed in these bags. Draw tape closures for large bags, and the manufacture of these draw tape bags are described in the aforesaid related U.S. Pat. Nos. 4,558,463 and 4,624,654. Other related patents are U.S. Pat. No. 4,617,008--Boyd et al which describes a hem forming apparatus and U.S. Pat. No. 4,597,750--Boyd et al which describes apparatus for inserting a draw tape into the bag. Bags having intermittently oriented draw tapes are disclosed in related U.S. Pat. No. 4,628,536--Herrington. The disclosure of the foregoing related patents are incorporated herein by reference.
In the past, thermoplastic bag structures with integral handle elements formed as an integral part of the bag structure itself have been produced by a method which reduces stress concentration. Stress points around the bag mouth are distributed to areas which are less likely to rupture as a result of stress concentration. See U.S. Pat. No. 4,165,832--Kuklies et al. This patent discloses a thermoplastic bag structure with integral handle elements, i.e. the handles are actually an extension of the bag proper and stress relief notches are positioned at opposite ends of the mouth. This patent also discusses the effect of "roping" while the bag is under load. Another technique that has been employed in the past in connection with integral handles of thermoplastic bags is to place patches of additional thermoplastic material around the handle openings. These patches are heat sealed or spot welded to the handle portions.
Draw tape bags have a draw tape that is a separate structure from the bag proper. Draw tape bags of the type made according to the above mentioned Boyd et al patents normally have a 1" wide draw tape for the full width of the bag. When the tape is pulled hard to close the bag, it elongates over most of its length and the area where it is gripped by the hand, becomes narrow, or "ropes" and hurts the hand. It is possible to make a draw tape that is sufficiently strong at thin gauges, such as 1.5 mils., but this tape is unsatisfactory for use because of the "roping" effect. As a result, it has been customary to use a tape material that is thicker, thus more costly than that which is required for performance. For example, tape thicknesses that have been used are in the order of 3 to 4 mils., about twice what is actually required.
It is desirable to produce a thermoplastic bag handle of a smaller gauge, less costly material, while substantially preventing "roping" at the area of the handle held by the hand of the carrier. It is also desirable to minimize the discomfort caused by roping by providing a hand-grip at the central area of the handle.
The following related patent applications disclose draw tape configurations for draw tape bags especially designed to reduce stress concentrations or "roping" and/or to provide a hand-grip at the hand are while the draw tape bag is under load.